Re: [PATCH 1/5] BIOS changes for configuring irq0->inti2 override (v4)

Beth Kon
2009-06-11T21:22:19Z

Sebastian Herbszt wrote:
> Beth Kon wrote:
>> These patches resolve the irq0->inti2 override issue, and get the
>> hpet working
>> on kvm.
>>
>> Override and HPET changes are sent as a series because HPET depends
>> on the
>> override. Win2k8 expects the HPET interrupt on inti2, regardless of
>> whether
>> an override exists in the BIOS. And the HPET spec states that in
>> legacy mode,
>> timer interrupt is on inti2.
>>
>> The irq0->inti2 override will always be used unless the kernel cannot
>> do irq
>> routing (i.e., compatibility with old kernels). So if the kernel is
>> capable,
>> userspace sets up irq0->inti2 via the irq routing interface, and adds
>> the
>> irq0->inti2 override to the MADT interrupt source override table,
>> and the mp table (for the no-acpi case).
>>
>> Changes from v3:
>>
>> - changes based on comments from Avi and Gleb.
>> - corrected legacy enable/disable for in-kernel PIT. The code now best
>> approximates a multiplexer that disables PIT interrupts when HPET is
>> in legacy mode (as described by HPET spec). Any changes to the PIT
>> that may occur while HPET is operating in legacy mode are saved, so
>> if HPET leaves legacy mode, the PIT is just reenabled, with mode
>> set to whatever the last setting from guest was. Legacy mode is
>> disabled
>> at least during crash and shutdown (in Linux), so this needs to be
>> handled properly.
>>
>>
>> ---
>> kvm/bios/rombios32.c | 60
>> ++++++++++++++++++++++++++++++++++++-------------
>> 1 files changed, 44 insertions(+), 16 deletions(-)
>
> What about the mptable entry count?
> Think it would need something like
>
> #ifdef BX_QEMU
> if (irq0_override)
> putle16(&q, smp_cpus + 17); /* entry count */
> else
> putle16(&q, smp_cpus + 18); /* entry count */
> #else
> putle16(&q, smp_cpus + 18); /* entry count */
> #endif
>
> Your patch "Fix non-ACPI Timer Interrupt Routing - v3" [1] included
> such a change.
>
> [1] http://lists.gnu.org/archive/html/qemu-devel/2009-04/msg01396.html
Yes, I lost that somehow! Thanks (again!).

>
> - Sebastian
>